Glass Fiber Composite Applications in New Energy Vehicles: Battery, PEU & Motor Insulation

In modern New Energy Vehicle (NEV) architecture, glass fiber composite materials—including epoxy fiberglass laminates (FR4/G10), SMC (Sheet Molding Compound), and specialized magnetic conductive sheets—have become vital engineered solutions. Rather than replacing metal structures indiscriminately, these materials are strategically deployed where electrical insulation, high dielectric strength, thermal barrier protection, and flame retardancy are mandatory.

This technical guide details the precise location-specific requirements and composite material selection across three core NEV subsystems: the Power Battery System, the Power Electronics Controller (PEU), and the Electric Drive Motor.

1. Power Battery Pack System: Structural Insulation & Thermal Protection

The power battery pack houses high-voltage DC circuits requiring rigorous dielectric isolation and passive fire protection during thermal runaway events. Glass fiber composites serve critical structural and insulating functions at key locations within the enclosure:

• Battery Enclosure Covers & Base Trays (SMC / Pultruded Composites): Compression-molded SMC (Sheet Molding Compound) covers provide lightweight structural protection with high impact resistance and flame retardancy.
  Material Requirements: Must meet UL 94 V-0 flame retardancy to delay thermal propagation, demonstrate low moisture absorption (≤ 0.40%) to prevent electrical leakage, and maintain dimensional stability under thermal cycling.
• Module Isolation Plates & Busbar Covers (FR4 / EPGC Sheets): Precision CNC-machined FR4 epoxy glass laminates are placed directly between battery cells and over high-voltage connection busbars.
  Material Requirements: Dielectric strength ≥ 12.0 kV/mm, High Comparative Tracking Index (CTI 600V) to eliminate arc tracking risks under high DC voltage, and precise thickness tolerance (±0.05 mm) for tight pack assembly.
• Cell Separation Barriers (High-Temperature Mica & FR4 Composites): Inter-cell insulation barriers prevent domino-effect thermal breakdown across adjacent lithium-ion cells.
  Material Requirements: Continuous temperature resistance from 130°C to 180°C (Class B to Class H) and zero halogen emission during combustion.

2. Power Electronics Unit (PEU) & Inverter: High-Voltage Isolation

The PEU converts DC power from the battery to AC power for the traction motor, operating at operating voltages often exceeding 400V–800V. Subsystem components demand high dielectric integrity and zero structural creep under mechanical vibration:

• Inverter Power Module Mounting Barriers & Substrate Supports: Flame-retardant unclad FR4 and G10 laminates form the insulating foundation beneath IGBT/SiC power modules and filter capacitors.
  Material Requirements: Exceptional flexural strength (≥ 350 MPa) to endure vehicle shock/vibration, high volume resistivity (≥ 1×10¹² Ω·cm), and strict flat tolerances to maintain consistent heatsink interface contact.
• High-Voltage Junction Box (HVJB) Interior Barriers: Machined composite partitions divide high-current busbars, fuse links, and contactors within compact junction boxes.
  Material Requirements: CTI 600V tracking resistance, UL 94 V-0 compliance, and continuous Class F (155°C) thermal degradation resistance.

3. Electric Drive Motor: Stator Slot Wedges & Phase Insulation

Traction motors in NEVs operate under elevated frequencies, high current densities, and tight thermal limits. Composite materials are deployed inside the stator slots and rotor assemblies:

• Stator Slot Wedges (EPGC308 / Glass Fiber Laminated Wedges): Driven into stator core slots to lock copper magnet wire windings against electromagnetic forces and vibration.
  Material Requirements: Class H (180°C) thermal rating (such as EPGC308 or H-class laminates), superior shear and flexural strength to prevent mechanical collapse, and resistance to ATF (automatic transmission fluid) or cooling oils in wet-rotor configurations.
• Magnetic Conductive Slot Wedges (H-Class Silicon Steel/Glass Composite Plates): Applied in high-efficiency permanent magnet motors to optimize magnetic flux distribution, reduce harmonic losses, and lower motor operating temperature.
  Material Requirements: High magnetic permeability paired with high interlaminar insulation resistance, engineered specifically to withstand thermal stresses up to 180°C.

Summary: Precise Material Specifications across NEV Subsystems